1. Field of the Invention
This invention relates to pneumatic tires, and more particularly, to a radial ply pneumatic tire in which the tread is rigidified and stabilized by an annular reinforcement belt.
2. Prior Art
Since the advent of the radial tire, it has been recognized that to enhance the operational characteristics of the tire, an annular reinforcement is necessary between the tire tread and the radial body cords of the tire carcass.
It has been found that the annular reinforcement has marked effects on the tread wear, road traction, resistance to lateral thrust and comfort of ride. Major problems, however, accompany these advantages. One of paramount importance is the tendency of the bond between the cords in the annular reinforcement and the surrounding rubber composition to deteriorate during high operational speeds.
In an attempt to alleviate the above and other problems, many different reinforcement belt structures have been proposed. For example, a reinforcement belt structure including two plies which do not extend beyond the tread width and a narrow ply which lies between the belt structure and the tire carcass is disclosed in U.S. Pat. No. 3,386,487. Variations of this structure can be seen in U.S. Pat. No. 3,717,190, and U.S. Pat. No. 3,735,790. In addition to the structures described in these patents, other reinforcement belt constructions have been devised containing combinations of plies of tire cord fabric having cords of steel and aromatic polyamide.
While each of the reinforcement belt structures described in the above cited patents attempts to alleviate the problems inherent in the radial tire construction, none of these arrangements make it possible to simultaneously achieve a radial pneumatic tire having resistance to longitudinal stress, improved lateral regidity, improved structural integrity at elevated operation speeds, and improved immunity to reinforcement belt separation.
It is toward the elimination of these and other problems that the present invention is directed.